Facsimile communications date back to well before the introduction of internet protocol (IP) technologies. Likewise, text telephony or teletype and modem communications were well established before IP technologies. In spite of recent trends of adapting modulated communication for transmission over IP networks, the underlying technologies remain analog, and challenges remain for modulated communications over IP networks. Accordingly, vendors, enterprises, and service providers have slowed the use of IP as a real-time fax transport.
Many of the challenges for modulated communication over IP networks stem from the differences between voice communications and modulated communications. For example, the optimal gain setting for modulated communications may be different than that of voice communications. A signal level may be clipped because of an improper gain setting. Voice communications, on the other hand, may not be noticeably degraded by the clipping because a clipped voice signal retains most of the voice spectrum and may simply sound louder. However, a modulated signal clipped at the same level may be degraded such that the modulated communications can no longer be decoded, resulting in a failure in the modulated communications.